In TypeScript, a union type variable is a variable which can store multiple type of values (i.e. number, string etc).
A union type allows us to define a variable with multiple types. The union type variables are defined using the pipe ('|'
) symbol between the types.
The union types help in some special situations. For example, when migrating from JavaScript code to TypeScript code.
1. Union Type Syntax
To define a union type, use the pipe symbol between multiple types which a variable should support.
let myVar: string | number; //myVar can store string and number types
2. Union Type Example
Let’s see an example of union type in TypeScript.
let myVar : string | number; //Variable with union type declaration myVar = 100; //OK myVar = 'Lokesh'; //OK myVar = true; //Error - boolean not allowed
Here, the myVar
variable can hold both number
and string
, which allows us to have the flexibility to use both data types.
The TypeScript compiler makes sure that it alerts us if we try to assign a type of value that was not defined.
Happy Learning !!
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